1. Field of the Invention
This invention relates to a high-strength, abrasion resistant aluminum alloy usable for sliding members, especially for vanes and rotors of rotary compressors, valve operating mechanisms of internal combustion engines, cylinders of magnetic heads, cylinders and pistons of miniature engines of model assemblies, pistons of engines and the like, and also to a method for processing the aluminum alloy.
2. Description of the Prior Art
In many instances, cast iron or alloyed steel is employed as a counterpart material for the sliding members described above so that the sliding members are used in combination with such a counterpart material.
The material employed for these members is, therefore, required to have excellent strength and heat resistance together with high abrasion resistance and also a coefficient of thermal expansion not too much different from the coefficient of thermal expansion of the counterpart material.
Among conventional aluminum alloys, Al--Si alloys are known as having excellent abrasion resistance. Among them, those having an Si content of 12-25 wt % are widely employed. Many of these materials are cast materials and, in order to exhibit abrasion resistance by coarse primary silicon crystals, coarse Si crystals of 20 .mu.m or greater are precipitated in the alloys.
The above-described cast Al--Si alloys are, however, accompanied by the problems that their sliding counterpart materials are subjected to more wearing by coarse primary silicon crystals and that they have low strength because they are cast materials. Further, processing operations are difficult--including cutting, cold working and warm working.
To improve the processability, it is necessary to reduce the Si content. A reduction in the Si content, however, leads to a greater coefficient of thermal expansion, resulting in the problem that difficulties are encountered in securing a suitable clearance relative to the sliding counterpart material.